The hallmark of human cognition is symbolization. In all societies, young children are expected to begin to master some of the various symbol systems that are necessary for full participation in their culture. Given the centrality of symbolization to human cognition and communication, it is important to study its origins and early development. a heuristic model of symbol understanding and use is presented and used to formulate hypotheses to be tested in the proposed studies. The proposed research falls into three general areas. Studies 1-5 investigate young children's understanding of 3-dimensional symbols, in particular their ability to u se a scale model as a representation and their ability to learn a novel symbol system. Studies 6-9 focus on children's ability to use a symbol (such as a doll) to represent themselves. These experiments are designed to have implications for the field of children's eyewitness testimony, and especially the use of dolls to interview young children in investigations of suspected child abuse. Studies 10-13 examine infants' and toddlers' understanding of the nature and representational function of pictures. The goals of the proposed studies are to (1) achieve a better understanding of the origins and early development of symbolic skills, (2) test and refine the model of symbolization with respect to the particular symbols for which it was originally developed, (3) begin to apply the model more broadly, and (4) produce results relevant to the design of educational materials and to the improvement of techniques for interviewing young children.